In recent years, home networks are being implemented in which AV appliances, such as a recording and reproducing apparatus, at home are connected to one another via a network so as to share various contents among the AV appliances.
Furthermore, in the case of handling data items required for copyright protection using the AV appliances, each of the AV appliances needs to be equipped with a processing means for protecting the copyright. The data items include recent movies, and fee-based TV programs and music. The most effective way to protect a copyright is to restrict the use of the data items required for copyright protection by encrypting the data items.
For example, as such a copyright protection protocol, Digital Transmission Contents Protection over Internet Protocol (DTCP-IP) has been put to practical use.
Under the DTCP-IP, 4 modes of copy control information have been defined which include “copy-free”, “copy-one-generation”, “no-more-copies”, and “copy never”. Based on the copy control information, copying of a content is restricted.
For example, when a recording and reproducing apparatus at home receives an AV data item of a program whose copy control information indicates “copy-one-generation” through broadcasting or distribution via the Internet and records the AV data item, the copy control information of the recorded AV data item is changed from the “copy-one-generation” to “no-more-copies” statuses. Thus, the AV data item recorded by the recording and reproducing apparatus is allowed for only its move. When the AV data item is recorded onto another recording and reproducing apparatus, the original AV data item is to be deleted. Thereby, copies of the AV data item cannot be created and used at home.
Meanwhile, the copyright protection protocols include a protocol in which the permitted number of copies of an AV data item is set as copy control information and whether or not copy is possible is managed based on the set number. In accordance with such a copyright protection protocol, with the permitted number of copies set as the upper limit, copies of the AV data item can be created and used (including the reproduction of the AV data item and creation of the additional copy) at home.
For example, PTL 1 discloses a technique regarding a digital content playback system that can appropriately copy or move a digital content whose permitted number of copies is restricted, between different devices.
With reference to FIG. 10, a conventional recording and reproducing apparatus will be described which can record a digital content whose permitted number of copies is restricted and create and use copies of the recorded digital content up to the permitted number of copies.
FIG. 10 conceptually illustrates that the conventional recording and reproducing apparatuses each of which can create and use the copies of an AV data item that is a digital content mutually transmit and receive the AV data item and information on each permitted number of copies by the apparatus, when they copy the AV data item via a home network.
In FIG. 10, recording and reproducing apparatuses 91 and 92 that are Hard Disk Drive (HDD) recorders and a recording and reproducing apparatus 93 that is a portable player are connected to one another via a home network 95.
Each of the apparatuses can copy an AV data item via the home network 95. Furthermore, each of the apparatuses has a function capable of converting a format of the AV data item when copying the AV data item.
Each of the recording and reproducing apparatuses 91 to 93 manages the permitted number of copies per AV data item. Each time it copies the AV data item, it subtracts 1 from a value indicating the permitted number of copies of the copied AV data item.
Furthermore, each of the recording and reproducing apparatuses 91 to 93 can move only their permitted number of copies of the AV data item held therein to another recording and reproducing apparatus.
In the example of FIG. 10, the permitted number of copies of a recorded program A held in the recording and reproducing apparatus 91 is “2” as a result of subtraction of “2” from “4”. Furthermore, the recording and reproducing apparatus 92 adds “2” indicating the permitted number of copies subtracted by the recording and reproducing apparatus 91, to “0” of the permitted number of copies of the recorded program A that is held by the recording and reproducing apparatus 92. As a result, the permitted number of copies of the recorded program A that is held by the recording and reproducing apparatus 92 is “2”.
Furthermore, when an apparatus to which an AV data item is copied (recording and reproducing apparatus) has a limitation in display capability and recording capability, generally, a format of the compression coding protocol is converted before the AV data item is copied.
[Citation List]
[Patent Literature]
    [PTL 1] Japanese Unexamined Patent Application Publication No. 2007-318669